Ultrathin film composite nanofiltration membrane was prepared in large-scale (1 m × 50 m) using indigenously developed casting and coating units. A spongy, nano-porous, compaction tolerant substrate layer (middle layer) was formed through judicial selection of the concentrations of base polymer (PSF) and its relative proportion with the pore former (PVP). The substrate with symmetric surface pore morphology (uniform distribution of innumerable nano-pores devoid of macrovoids) facilitated the formation of ultrathin polyamide rejection layer much in the form of laminate (of near uniform thickness) with very limited penetration to the substrate pores. The polyamide layer thickness could be down to 40 nm for the NF/PS/8PVP membrane. XPS study revealed a co-existence of polyamide cross-linked network and linear portion comprised of many sub-units with terminal carboxylic acid groups, which impart surface hydrophilicity and potential. The membranes exhibit a trade-off relationship between flux and selectivity with a flux of 158 L M⁻²H⁻¹ at 50 psi and Na₂SO₄ rejection of >99% for NF/PS/8PVP membrane.

超薄膜复合纳滤膜采用自主开发的浇注和涂层装置大规模制备（1 m × 50 m）。通过合理选择基础聚合物 (PSF) 的浓度及其与造孔剂 (PVP) 的相对比例，形成海绵状、纳米多孔、耐压实的基底层（中间层）。具有对称表面孔形态的基材（无数纳米孔的均匀分布，没有大空隙）促进了超薄聚酰胺排斥层的形成，这种超薄聚酰胺排斥层非常以层压板（几乎均匀的厚度）的形式形成，对基材孔的渗透非常有限。NF/PS/8PVP 膜的聚酰胺层厚度可低至 40 nm。XPS研究揭示了聚酰胺交联网络和由许多具有末端羧酸基团的亚单元组成的线性部分共存，从而赋予表面亲水性和潜力。膜在通量和选择性之间表现出权衡关系，通量为 158 L M^-2 H ^-1在 50 psi 和 Na ₂ SO ₄对 NF/PS/8PVP 膜的截留率 >99%。